inverted index for a
collection of documents is a structure that stores, for each term (word)
occurring somewhere in the collection, information about the locations where it
occurs. In particular, for each term t, the index contains an inverted list It
consisting of a number of index postings. Each posting in It contains
information about the occurrences of t in one particular document d, usually
the ID of the document (the docID), the number of occurrences of t in d (the
frequency), and possibly other information about the locations of the
occurrences within the document and their contexts. The postings in each list
are usually sorted by docID.